Micromechanical rotation system with coupled actuators

Abstract

The present invention is directed towards a system for rotating a pedestal through the use of rotatable actuators. First and second rotatable actuators having substantially parallel rotation axes are connected to the pedestal via linkage arms and gimbal springs. A coupling mechanism inhibits the first and second rotatable actuators from simultaneously rotating in the opposite sense about their respective axes.

What is claimed is:  
     
       1. An apparatus, comprising: 
       a pedestal;  
       a first rotatable actuator having a first actuator rotation axis;  
       a second rotatable actuator having a second actuator rotation axis, the second actuator rotation axis being substantially parallel to the first actuator rotation axis, the first actuator rotation axis and the second actuator rotation axis defining an actuator plane;  
       a first linkage arm attached to the first rotatable acutator;  
       a second linkage arm attached to the second rotatable actuator;  
       a first gimbal spring connecting the first linkage arm to the pedestal, the first gimbal spring having a first gimbal spring effective pivot;  
       a second gimbal spring connecting the second linkage arm to the pedestal, the second gimbal spring having a second gimbal spring effective pivot; and  
       a coupling mechanism that inhibits the first rotatable actuator and the second rotatable actuator from simultaneously rotating in the opposite sense about their respective axes.  
     
     
       2. The apparatus, according to  claim 1 , wherein the coupling mechanism comprises: 
       a first standoff column mounted on the first rotatable actuator;  
       a second standoff column mounted on the second rotatable actuator; and  
       a flexure joining the first standoff column and the second standoff column.  
     
     
       3. The apparatus, according to  claim 2 , wherein the flexure is thin in the direction perpendicular to the actuator plane relative to its dimensions parallel to the actuator plane. 
     
     
       4. The apparatus, according to  claim 3 , further comprising: 
       a post mounted on the pedestal; and  
       a mirror mounted on the post.  
     
     
       5. The apparatus, according to  claim 4 , wherein the mirror is substantially flat and lies in substantially the same plane as the flexure. 
     
     
       6. The apparatus, according to  claim 2 , further comprising: 
       a third rotatable actuator having a third actuator rotation axis;  
       a fourth rotatable actuator having a fourth actuator rotation axis, the fourth actuator rotation axis being substantially parallel to the third actuator rotation axis, the first actuator rotation axis and the third actuator rotation axis being substantially perpendicular;  
       a third linkage arm attached to the third rotatable acutator;  
       a fourth linkage arm attached to the fourth rotatable actuator;  
       a third gimbal spring connecting the third linkage arm to the pedestal; and  
       a fourth gimbal spring connecting the fourth linkage arm to the pedestal.  
     
     
       7. The apparatus, according to  claim 1 , wherein the coupling mechanism comprises: 
       a first standoff column mounted on the first rotatable actuator;  
       a second standoff column mounted on the second rotatable actuator;  
       a first compliant hinge connected to the first standoff column, the first compliant hinge being disposed a first standoff height from the first rotatable actuator;  
       a second compliant hinge connected to the second standoff column, the second compliant hinge being disposed a second standoff height from the second rotatable actuator;  
       a coupling bar joining the first compliant hinge to the second compliant hinge.  
     
     
       8. The apparatus, according to  claim 7 , wherein the coupling bar is substantially rigid. 
     
     
       9. The apparatus, according to  claim 7 , wherein the coupling mechanism increases the torque required to rotate the first and second rotatable actuators in the opposite sense about their respective axes without substantially increasing the torque required to rotate the first and second rotatable actuators in the same sense about their respective axes. 
     
     
       10. The apparatus, according to  claim 7 , wherein the first compliant hinge is thinner in one dimension parallel to the actuator plane than perpendicular to the actuator plane. 
     
     
       11. The apparatus, according to  claim 10 , wherein the second compliant hinge is thinner in one dimension parallel to the actuator plane than perpendicular to the actuator plane. 
     
     
       12. The apparatus, according to  claim 7 , further comprising: 
       a post mounted on the pedestal; and  
       a mirror mounted on the post.  
     
     
       13. The apparatus, according to  claim 12 , wherein the mirror is substantially flat and lies in substantially the same plane as the coupling bar. 
     
     
       14. The apparatus, according to  claim 7 , wherein the first compliant hinge is a serpentine spring. 
     
     
       15. The apparatus, according to  claim 14 , wherein the serpentine spring comprises a plurality of spring legs coupled in series, each spring leg being thinner in one dimension parallel to the actuator plane than perpendicular to the actuator plane. 
     
     
       16. The apparatus, according to  claim 15 , further comprising: 
       a post mounted on the pedestal; and  
       a mirror mounted on the post.  
     
     
       17. The apparatus, according to  claim 16 , wherein the mirror is substantially flat and lies in substantially the same plane as the coupling bar. 
     
     
       18. The apparatus, according to  claim 7 , further comprising: 
       a third rotatable actuator having a third actuator rotation axis;  
       a fourth rotatable actuator having a fourth actuator rotation axis, the fourth actuator rotation axis being substantially parallel to the third actuator rotation axis, the first actuator rotation axis and the third actuator rotation axis being substantially perpendicular;  
       a third linkage arm attached to the third rotatable acutator;  
       a fourth linkage arm attached to the fourth rotatable actuator;  
       a third gimbal spring connecting the third linkage arm to the pedestal; and  
       a fourth gimbal spring connecting the fourth linkage arm to the pedestal.  
     
     
       19. The apparatus, according to  claim 7 , wherein: 
       the first compliant hinge has a first hinge rotational stiffness relating applied torque to angular rotation about an axis parallel to the first actuator rotation axis, the first hinge rotational stiffness being denoted K c1 ;  
       the second compliant hinge has a second hinge rotational stiffness relating applied torque to angular rotation about an axis parallel to the second actuator rotation axis, the second hinge rotational stiffness being denoted K c2 ;  
       the first compliant hinge has a first hinge in-plane displacement stiffness relating applied force to displacement substantially parallel to the actuator plane and directed substantially along a line joining the first and second compliant hinges, the first hinge in-plane displacement stiffness being denoted by K cx1 ;  
       the second compliant hinge has a second hinge in-plane displacement stiffness relating applied force to displacement substantially parallel to the actuator plane and directed substantially along a line joining the first and second compliant hinges, the second hinge in-plane displacement stiffness being denoted by K cx2 ;  
       a first linkage length is defined as the distance from the first actuator rotation axis to the first gimbal spring effective pivot, the first linkage length being denoted L 1 ;  
       a second linkage length is defined as the distance from the second actuator rotation axis to the second gimbal spring effective pivot, the second linkage length being denoted L 2 ;  
       the first standoff height is denoted by R 1 ;  
       the second standoff height is denoted by R 2 ; and  
       the ratio (K cx1 (R 1 /L 1 ) 2 +K cx2 (R 2 /L 2 ) 2 )/(K c1 /L 1   2 +K c2 /L  2   2 ) is greater than 1.  
     
     
       20. The apparatus, according to  claim 19 , wherein: 
       the ratio (K cx1 (R 1 /L 1 ) 2 +K cx2 (R 2 /L 2 ) 2 )/(K c1 /L 1   2 +K c2 /L 2   2 ) is greater than 10.  
     
     
       21. The apparatus, according to  claim 7 , wherein: 
       the first compliant hinge has a first hinge rotational stiffness relating applied torque to angular rotation about an axis parallel to the first actuator rotation axis, the first hinge rotational stiffness being denoted K c1 ;  
       the second compliant hinge has a second hinge rotational stiffness relating applied torque to angular rotation about an axis parallel to the second actuator rotation axis, the second hinge rotational stiffness being denoted K c2 ;  
       the first compliant hinge has a first hinge in-plane displacement stiffness relating applied force to displacement substantially parallel to the actuator plane and directed substantially along a line joining the first and second compliant hinges, the first hinge in-plane displacement stiffness being denoted by K cx1 ;  
       the second compliant hinge has a second hinge in-plane displacement stiffness relating applied force to displacement substantially parallel to the actuator plane and directed substantially along a line joining the first and second compliant hinges, the second hinge in-plane displacement stiffness being denoted by K cx2 ;  
       a first linkage length is defined as the distance from the first actuator rotation axis to the first gimbal spring effective pivot, the first linkage length being denoted L 1 ;  
       a second linkage length is defined as the distance from the second actuator rotation axis to the second gimbal spring effective pivot, the second linkage length being denoted L 2 ;  
       the first standoff height is denoted by R 1 ;  
       the second standoff height is denoted by R 2 ;  
       the first gimbal spring has a first gimbal spring rotational stiffness measured about an axis parallel to the first actuator rotation axis, the first gimbal spring rotational stiffness being denoted K g1 ;  
       the second gimbal spring has a second gimbal spring rotational stiffness measured about an axis parallel to the second actuator rotation axis, the second gimbal spring rotational stiffness being denoted K g2 ;  
       a pedestal x-rotation axis is defined as the axis of rotation of the pedestal in response to same-sense rotations of the first and second rotatable actuators;  
       a first pedestal distance is defined as the distance from the first gimbal spring effective pivot to the pedestal x-rotation axis, the first pedestal distance being denoted by D 1 ;  
       a second pedestal distance is defined as the distance from the second gimbal spring effective pivot to the pedestal x-rotation axis, the second pedestal distance being denoted by D 2 ; and  
       the ratio (K cx1  R 1   2 +K cx2  R 2   2 )/{(L 1 /D 1 )(2+(L 1 /D 1 ))K g1 +[(L 2 /D 2 )(2+(L 2 /D 2 ))]K g2 +(K c1 +K c2 )} is greater than 1.  
     
     
       22. The apparatus, according to  claim 21 , wherein: 
       the ratio (K cx1  R 1   2 +K cx2  R 2   2 )/{(L 1 /D 1 )(2+(L 1 /D 1 ))K g1 +[(L 2 /D 2 +(L 2 /D 2 ))]K g2 +(K c1 +K c2 )} is greater than 10.